| 摘要 |
PURPOSE:To prevent overheating of parts constituting an inverter circuit and that of a stabilizing element by detecting the instantaneous value of pulsating voltage departing from the specified range, which occurs when the emitter of a filament consumes and the life of a discharge lamp becomes the close, by means of a pulsating voltage detection circuit so as to suppress the oscillation of the inverter circuit. CONSTITUTION:If either emitter of the filaments F1 and F2 of a discharge lamp FL consumes and the life of the lamp FL becomes the close, it becomes hard for currents to flow to the lamp FL, and instead the currents begin to flow to an inverter circuit IN through an impedance element C2. At this time, as the impedance of the element C2 is smaller than the impedance value of the lamp FL, the output current of the circuit IN increases than that when the lamp FL is normal and also the amplitude becomes large. Accordingly, the amplitude width of pulsating flow voltage which appears at the power source side electrode terminal of the filament F2 and on the negative electrode side of a DC power source E increases, so the departure of an instantaneous value is detected using a pulsating flow voltage detection circuit MR1, and the oscillation of the circuit IN is suppressed or stopped. |
